Apparatus for burning refuse fuel



Feb. 16, 1960 Filed July ll. 1955 E. C. MILLER Ev-TAL APPARATUS F'OR BURNING REFUSE FUEL 3 Sheets-Sheet 1 IN VEN TOR5 HARO D HA/vsafv EAR/ E C. Mu 1. El? CEDH/c: H. 5 roNE Feb. 16, 1950 E. c. MILLER ETAI- 2,925,055

APPARATUS FOR BURNING REFUSE: FUEL Filed July 1l. 1955 I5 Sheets-Sheet 2 y l I l r l I 4! 4Z 43 44 45 4e u www W f@ Vlam x i D J7 k57/ INVENTUM HAROLD Ha/50N EQRLE C. M/LER CEDRIC HSTONE Feb. 16, 1960 E. c. MILLER ETAL APPARATUS Foa BURNING REEusE FUEL 3 Sheets-Sheet 5 Filed July 11. 1955 mem www

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wem 01T T W HEC f M1/NJW I H orney United StatCS Paten/ff() 'APPARATUS `.Eon BURNlNG REFUSE FUEL Earle C. Miller, Worcester, Mass., and Cedric A. Stone `and Harold Hansen, Canton, N.C., assignors, by direct and nesne assignments, to Riley Stoker Corporation, Worcester, Mass., a corporation of Massachusetts application July 11, 1955, serialNo. 521,068 `s Claims. y`(c1. 11o-105) lfor instance, .the bark which has been removed from the pulp logscontains a` considerable amount of heat value which, if used, would enter advantageously into the economic balance of the industry. Like many of these refuse fuels, however, such bark contains a large amount Vof Aforeign matter. The bark, of course, may be wet and .it may be mixed with sand,'di`rt, and other types of material of vsimilar nature. Itis desirable to fire this vbark Without processing it, since a comminuting apparatus for reducing it to small Auniform pieces `means added expense for the initial installationand added maintenance costs. However, the unprocessed bark is a heterogeneous mixture containing `long pieces, short pieces, lengths of fiber, sawdust, and the like.` The non-homogenous nature of this type of fuel makes it difficult to burn,` but thespreader stoker is'particularly adapted to this function `in that it provides for the burning of the liner particles in suspension and the burning lof coarser particles on the grate. However, this fuel presents additionalproblems. For instance, in most paper mills and the like, the arrival ofthe refuse material to `the site of the steam generating unit is sporadic and, once having arrived, it is ditlicult to -distribute'it properly over the surface of the grate for burning. These and other difficulties experienced with the priorart have been obviated by the present invention in a novel manner. c

. Itis `therefore an outstanding object of the invention to provideapparatus for the burning of refuse fuel which apparatus is .rugged and dependable and inexpensive Vto manufacture. c,

It is another object of this invention to provide apparatus for the burning of bark and the like which provides for uniform distribution of the bark over the grate surface.` c c `A still Yfurther object of the present `invention is `the `provisionof. apparatusfor burning bark and the like ,for use with a steam generating unit wherein the heat release necessary `for the generation of a preselected amount of steam is maintained constant, irrespective of uctuations inthesupply of refuse fuel.

It Vis a further object of the instant invention to provide apparatus for burnngrefuse fueland a conventional solid fuelsuchl as coal in thesamefurnace of a steam generating unit.

To the accomplishmentof the foregoing and related ends, the invention then comprisesthe features hereinafterifully described and particularly pointed out in the claims.` l

]The following description and the annexed drawings setting forth in detail certain illustrative embodiments of theixivention, these being indicative, however, of but a Patented Feb. 16, 1,960

2 few of the various ways in which Ytheprincples `of the invention may be employed.

In said annexed drawings:

Figure 1 is a longitudinal `sectional view of a steam generating unit embodying the principles of the present invention,

Figure! is a `front elevational lview of aportion of the apparatus shown in Figure 1.,

Figure 3 vis a vertical, sectional View of a Arotary distributor, c v

Figure 4 is a top view of the distributor, and

` Figure 5 is a horizontal sectional view ofthe distributor taken on the line-vl-V of Figure 3.

Referring rst to Figure 1, wherein is best shown 4the general features of the' invention, the apparatus `of the invention, indicated generally by the reference numeral 1.0, is shown in use with a furnace. 11 and a boiler 12. The furnace 11 `comprises a front wall 13, a rear wall 14, and `side walls 1S defining a combustion chamber 16. At the bottom of the combustionl chamber fis a traveling grate 17 which may be of the endless chain type. .An air plenum [chamber 18 underlies the grate 17 and is .provided with air through a duct 19. The boiler 1,2 comprisesla steam and water drum 20 .and a lower drum `21 vjoined by downcorner tubes 22 and steam tubes 23. Large downcorner tubes 24 supply water wall tubes 2S with` the.V operating `fluid. Situated in an upper pass of the boiler isa 4superheater 26 connected at one end to ,steamyreieasespace of the steam and water drum 20 and at the other end to a superheated steamV header 27. The :steam generating unit is further provided with an "econornizer ZSand an air heater 29 of the usual type. The gas `outlet ofthe air'heateris connected to a dust vcollector 36 which, in turn, is connected through an inducedgdraft` fan 3,1 to a` stack 32. Cinder hoppers 33 and ,3.4 are `provided in the lower part of the boiler underlying the tubes 22, 23, andthe superheater 26. The dust `collector 30, the cinder hopper 33, and the cinder hopper 34 are connected respectively by conduits 35, 36, and 37 to an attrition type pulverizer 38. The output of the pulverizer is connected through a conduit 39 to reinjection nozzles 40situated in the rear wall 14 of the furnace .11. l

vSituated `in Vthe front wall 13 of the furnace 11 are a number of pneumatic spreader stokers 41, 4Z, 43, 44, 45, and 46. These spreader stokers are of the general type shown andudescrvibed in Patent No. 2,602,706, issued to Miller onJuly 8,V 1952. The pneumatic spreaders 41, 42, 43, 44, 45, and 46 are `connected by chutes 47, 43, 49 50, `51,'and 52 respectively to a fuel Vproportioner 53.

l rl`he proportioner 53 isof-ta known type having a rotary element which presents an opening to the ducts one at a time `in turn.` The ducts are attached to the bottom of `the proportioner 53 in a circle and the diverting element of the proportioner 53 directs fuel to the ducts one at a time,`as will be described more fully hereinafter. The entrance tothe proportioner 53 is connected through `a fuel weighing mechanism` 54 to a duct S5 leading to a source of refuse fuel. Each of Athe chutes is provided withwa damper 56 for cutting olf fuel flow therethrough.

`Onthe front wall 13 of the furnace 11 and situated between the pneumatic spreader stokers and the grates 17 are a series of mechanical spreader stokers 57. These stokers are of the type shown and described in Patent No. 2,538,944, `issued to Miller on January 23, 1,951. This type of Stoker contains a rotary distributor and fuel ow regulating mechanism and is particularly adapted to use with asolid conventional fuel such as coal. Each spreader stoker 57 is connected by a chute 58 to a feeding mechanism 59 and the input of the feeding mechanism is connected `by a duct 60 to a `source of conventional fuel not shown.

sensitive- 'element' 6'1" situated in the superheated-steam` a signal to the regulator 63 through a conduit 64 con nected thereto. The output of the regulator 63 is connected through conduits to an actuator 65 which is connected `to a lever 66 which lever is the speed control lever of the feeder 59.

It should be particularly noted that the ducts 47, 48, 49, 50, 51, and 52 which connect the pneumatic spreader stokers 41, 42, 43, 44, 45, and 46 respectively vto the proportioner 53 are connected at their upper ends to the bottom of the proportioner in such a manner that they lie in a circle in the following sequence: '47, 50, 48, 51, 49, 52. This means that as the revolving element of the proportioner 53 revolves, fuel will be distributed to orare carried by the ow of gases upwardly through lthe'combustion chamber and "burn during their passage the pneumatic spreaders in the following order: 41, 44, l

'42, 45,-43, 46. l -Referring to Figures 3. 4, and 5, the distributor'53 is shownas being ofa well-known type having an upper rotary l'portion 71 mounted lover a stationary portion 72. Thetop of the upper portion 71 resides at the lower end of the chute'extending downwardly from the fuel-weighing mechanisn1'54.` The lower portion is divided into compartments by radial walls 73, each compartment being connected at its lower portion to one of the ducts 47 through 52 as indicated by the reference numerals y portion of the lower end.V The upper portion is driven by a' motor 75 through a reduction unit 76, a shaft 77, Vand a vertical shaft 78.

The loperation ofthe apparatus will now be clearly understood -in` view of the` above description. Fuel which is burned in the combustion chamber 16 of the furnace 11 will pass upwardly through the boiler 12 and generate steam in the tubes thereof. The steam will be superheated in the superheater 26 and will eventually arrive at the superheater header 27. After passing through the boiler 12, the'gases'will pass through the economizer 28, the air heater 29, the dust collector 30, the induced draft fan 31, and the stack,32. Ash, which is not burned in suspension, will fall on the grates 17, the surface of which move slowly-toward the ash pit and all ash will be deposited in that ash pit. Unburned particles of fuelwhich pass through the boiler surfaces will be collected in the dust collector 30, the cinder hopper 33, `and the cinder hopper 34. These particles will passthrough the conduits 35, 36, and 37 and enter the pulverizer 38. The pulverizer will reduce large unburned upward. Heavier particles fall onto the grate 17 and burn there in the usual manner. On occasion, when the arrival of refuse fuel at the apparatus is insuicieut to maintain the desired production of steam, the refuse fuel may be supplemented by conventional solid fuel such as coal. The coal enters the duct 60,V passing through the feeder 59. The coal passes from .the feeder 59 into the d uct 58 to the mechanical spreader stokers 57.- The rate of coal feed through feeder 59 is regulated by the angular aspect of the control lever 66.

It will be understood, then, that refuse fuel entering the combustion chamber 16 will be introduced alternately on widely-separated portions of the grate 17. When this is done in the manner recited above', the distribution of bark on the grate is very even. There is no tendency for the refuse fuel to accumulate in one place with a resultant failure of ignition and slow combustion. The optimum situation, of course, is to have the refuse fuel spread in an even thin layer all over the surface of the-grate 17. This subjects the optimum amount of the fuel to the direct radiation of the furnace walls, and furthermore, assures that the air ow from the plenum chamber 18 through the gratev and through the fuel is the same for each particle of the fuel. The control system is based on the requirement that the bark must be burned directly as it is received at a fluctuating rate and that coal must be burned to supplement the barky when bark flow drops below a set minimum level or stops completely; This method insures against loss of ignition during'periods of no bark ow and is used to supplement plant steam capacity. VTo obtain'this type of control action, the duct 55 which discharges to the' proportioner 53 has a calibrated weight integrater or fuel weighing apparatus 54, which sends an impulse through the conduit 64 to the regulator 63. The coal feed rate is established by a splitter relay which balances steamowvand coallfeed rate against. the minimum load setting. In other wordsr, when the weighing apparatus .54 indicates to the regulator 63 that the ow of bark to the system is low, the regulator 63 sets the actuator 65 in motion to turn the control lever 66 and change the setting of the feeder 59. The

particles to a sm-aller `size and they will passthrough the conduit 39 and from the nozzles 40 into the combustion chamber again for burning. Refuse fuel, such as bark, enters the apparatus through the duct and ,passes throughthe refuse fuelweighing apparatus 54. This apparatus continually weighs and intergrates the fuel entering the apparatus and sends a signal through the conduit 64 which is representative of the amount of fuel entering the system. The refuse fuel then passes into the proportioner 53 andV its rotary element turns in the usual manner distributing fuel to the ducts 47, 48, 49,

50, 51, and 52. `Because Yof, the construction of the proportioner Vand the 'attachment of the ducts to the proportioner, ashas been described above, the fuel will be distributed in equal amounts to each `duct in the following order: duct 47, duct 50, duct 48, duct 51, duct 49, duct 52, and so on. This means that the pneumatic spreader stokers will receive the fuel inthe following order: Stoker 41, stoker 44, stoker 42, stoker 45, stoker 43, stoker 46', and so on. The air supplied to the pneumaticstokers blows the bark or other fuel out into the combustion chamber 16. Thelighter particles ignite immediately and burn before they reach the grate 17,

connection is such as to increase the'tlow of coal into the .stokers 57. when the flow o f refuse fuel through the weighing apparatus 54 is lowered. The regulator 63 also sends an impulse to the actuator which is connected g to the damper in the duct 19 leading to the air plenum chamber 18. The signal is related to the amount of refuse fuel entering the system in such a manner that the air ow through the grate is always the exact amount necessary with the given proportion of coal to refuse fuel. This is necessary because of the fact that burning 100% refusefuel requires an entirely different amount of air flow through Vthe grate than burning 100% coal and there is an optimum air flow for any given proportion of these fuels.

Other modes of applying the principles of the invention may be employed, change being made as regards the details described, provided the features statedin'the following clainis, or the equivalent of such, be employed. The invention having thus been described, what is claimed as new and desired to secure by Letters Patent is:

1. Apparatus for burning refuse fuel in a steam generating unit comprising a furnace, the furnace having a grate bottom, and a series of pneumatic spreader stokers mounted side by side at a considerable distance above the grate to project refuse fuel into the furnace, the fine pardelivery.l of-'refuse fuel to the pneumatic. spreader stokers beingin' a regular predetermined sequence of first, fourth, second, fifth, third, and-sixth positions. toassure even. disti'ibutionl of the-refuse fuel. upon the4 grate.

2. Apparatus forburing refusez fuell in a steam` generatingimit comprising` a` furnace havinga grate bottom, comprising a series of pneumaticspreaderpstokersV mounted side by side at a considerable distance above the grate to project refuse fuel into the furnace, the line particles being burned in suspension and larger particles falling onto the grate, a refuse fuel proportioner, a duct connecting each pneumatic spreader stroker to the proportioner, the ducts being connected to the proportioner so that fuel is delivered to one duct at a time, the pneumatic spreader stokers occupying, first, second, third, fourth, fifth, and sixth positions across the grate, the order of delivery of refuse fuel to the pneumatic spreader stokers being in a regular predetermined sequence of fifth, fourth, second, fifth, third, and sixth positions to assure even distribution of the refuse fuel upon the grate, a series of mechanical spreader stokers mounted to project a conventional solid fuel into the furnace, a feeder for the feeding of conventional fuel to the mechanical spreader stokers, a weighing apparatus for indicating the rate of feeding of refuse fuel to the pneumatic spreader stokers, and a regulator for adjusting the feeder with changes in the indication of the weighing apparatus.

3. Apparatus for burning refuse fuel in a steam generating unit comprising a furnace and a boiler, the furnace having a grate bottom, comprising a series of pneumatic spreader stokers mounted side by side at a considerable distance above the grate to project refuse fuel into the furnace, the fine particles being burned in suspension and the larger particles falling onto the grate, a refuse fuel proportioner, a duct connecting each pneumatic spreader stoker to the proportioner, the ducts being connected to the proportioner so that fuel is delivered'to one duct at a time, the pneumatic spreader stokers occupying first, second, third, fourth, fifth, and sixth positions across the grate, the order of delivery of refuse fuel to the pneumatic spreader stokers being in a regular predetermined sequence of first, fourth, second, fifth, third, and sixth positions to assure even distribution of the refuse fuel upon the grate, collector means for accumulating unburned particles of fuel, a puverizer, conduit means for conveying the said unburned particles to the pulverizer for comminution, reinjection nozzles mounted in the furnace, and

means for delivering the said comminuted particles to the nozzles.

4. Apparatus for burning refuse fuel in a steam generating unit comprising a furnace having a grate bottom and a series of pneumatic spreader stokers mounted side by side at a considerable distance above the grate to project refuse fuel into the furnace, the fine particles being burned in suspension and the larger particles falling onto the grate, a refuse fuel proportioner, a duct connecting each pneumatic spreader stoker to the proportioner, the ducts being connected to the proportioner so that fuel is delivered to one duct at a time, the pneumatic spreader stokers occupying first, second, third, fourth, fifth, and sixth positions across the grate, the order of delivery of refuse fuel to the pneumatic spreader stokers being in a regular predetermined sequence of first, fourth, second, fifth, third, and sixth positions, to assure even distribution of the refuse fuel upon the grate, a series of mechanical spreader stokers mounted to project a conventional solid fuel into the furnace, a feeder for the feeding of conventional fuel to the mechanical spreader stokers, a weighing apparatus for indicating the rate of feeding of refuse fuel to the pneumatic spreader stokers, and a regulatoi for adjusting the feeder with changes in the indication of the weighing apparatus, collector means for accumulating unburned particles of fuel which pass through the boiler, a pulverizer, conduit means for conveying the said unburned particles to the pulverizer for comminution, reifnjectionrl nozzles mounted in the furnace, anclv means for delivering the said comminuted particles to the nozzles.

5. Apparatus for burning refuse fuel in a steam generating unit comprising a grate-bottomed furnace having a series of pneumatic spreader stokers mounted to project refuse fuel into `tli`e` furnace, a rotary refuse fuel proportioner having a series of ducts arranged in a circle about the axis of rotation, the proportioner rotating in one direction only, one of the said ducts connecting each pneumatic spreader stoker to the proportioner, the ducts connected to the proportioner so that fuel is delivered to one duct at a time, the order of delivery of refuse to the pneumatic spreader stokers being in a regular pre-determined sequence to assure even distribution of the refuse fuel upon the grate, equal periods of time elapsing between one delivery of fuel to any given stoker and the :next delivery of fuel to the same Stoker.

6. Apparatus for burning refuse fuel in a steam generating unit comprising a furnace having a series of primary fuel-feeding means mounted to project refuse fuel into the furnace, a refuse fuel proportioner, a duct connecting each primary fuel-feeding means to the proportioner, the ducts being connected to the proportioner so that fuel is delivered to one duct at a time, the order of delivery of refuse fuel to the series of primary fuel-feeding means being at a regular pre-determined sequence to assure even distribution of the refuse fuel to various parts of the furnace, equal periods of time elapsing between one delivery of fuel to any given primary fuel-feeding means and the next delivery of fuel to the same primary fuel-- feeding means, secondary fuel-burning means mounted to burn a conventional fuel in the furnace, and means relating to the feeding of conventional fuel to the said secondary fuel-burning means to make up for the reduction of feeding of refuse fuel to the series of primary fuel-feeding means.

7. Apparatus for burning refuse fuel in a steam generating unit comprising a grate-bottomed furnace having a series of pneumatic spreader stokers mounted to project refuse fuel into the furnace, a rotary refuse fuel proportioner having a series of ducts extending downwardly therefrom and arranged in a circle about the axis of rotation of the proportioner, the proportioner rotating continuously at constant speed in one direction only, one of the said ducts connecting each pneumatic spreader Stoker to the proportioner, the ducts being connected to the proportioner so that fuel is delivered to one duct at a time, the order of delivery ofrefuse fuel to the pneumatic spreader stokers being in a regular pre-determined sequence to assure even distribution of the refuse fuel upon the grate, equal periods of time elapsing between one delivery of fuel to any given pneumatic stoker and the next delivery of fuel to the same pneumatic stoker, a series of mechanical spreader stokers mounted to project the conventional solid fuel into the furnace, means relating the feeding of conventional' fuel to the mechanical spreader stokers to make up for the reduction of feeding of refuse fuel to the pneumatic spreader stokers.

8. Apparatus for burning refuse fuel in a steam generating unit comprising a furnace having a grate-bottom and a series of pneumatic spreader stokers mounted sideby-side at a considerable distance above the grate to project refuse fuel into the furnace in a regular pre-determined sequence, equal periods of time elapsing between the delivery of fuel to the grate by one pneumatic Stoker and the next delivery of fuel by the same Stoker, the fine particles being burned in suspension and the larger particles falling onto the grate, a series of mechanical spreader stokers mounted to project a conventional solid fuel into the furnace, a feeder for the feeding of conventional fuel to the mechanical spreader stokers, a weighing apparatus for indicating the rate of feeding of refuse fuel to the pneumatic spreader stokers, and a regulator for adjustng the feeder with changes in the indication of the weighing apparatus.

- References Cited in the le of this patent I UNITED STATES PATENTS Baggaley Apr. 15, 1904 Daniels Jan. 9, 1934 Sparks Aug. 17, 1954 quan- 

